Settable compositions comprising cement kiln dust and swellable particles

ABSTRACT

A variety of methods and compositions are disclosed herein, including, in one embodiment, a method comprising: introducing a settable composition into a subterranean formation, wherein the settable composition comprises: a cementitious component comprising a hydraulic cement and cement kiln dust; a swellable particle; and water; and allowing the settable composition to set in the subterranean formation. Another embodiment comprises a settable composition comprising: a cementitious component comprising a hydraulic cement and cement kiln dust; a swellable particle; and water.

BACKGROUND

This application is a continuation-in-part of U.S. patent applicationSer. No. 11/223,669, entitled “Settable Compositions Comprising CementKiln Dust and Additives(s),” filed Sep. 9, 2005, the entire disclosureof which is hereby incorporated by reference.

BACKGROUND

The present invention relates to cementing operations and, moreparticularly, to settable compositions comprising hydraulic cement,cement kiln dust (“CKD”), swellable particles, and water and associatedmethods of use.

Settable compositions may be used in a variety of subterraneanapplications. As used herein, the term “settable composition” refers toany composition that over time will set to form a hardened mass. Oneexample of a settable composition comprises hydraulic cement and water.Subterranean applications that may involve settable compositionsinclude, but are not limited to, primary cementing, remedial cementing,and drilling operations.

Settable compositions may be used in primary cementing operationswhereby pipe strings, such as casing and liners, are cemented in wellbores. In performing primary cementing, a settable composition may bepumped into an annular space between the walls of a well bore and thepipe string disposed therein. The settable composition sets in theannular space, thereby forming an annular sheath of hardened cement(e.g., a cement sheath) that supports and positions the pipe string inthe well bore and bonds the exterior surface of the pipe string to thewalls of the well bore.

Settable compositions also may be used in remedial cementing operations,such as sealing voids in a pipe string or a cement sheath. As usedherein the term “void” refers to any type of space, including fractures,holes, cracks, channels, spaces, and the like. Such voids may include:holes or cracks in the pipe strings; holes, cracks, spaces, or channelsin the cement sheath; and very small spaces (commonly referred to as“microannuli”) between the cement sheath and the exterior surface of thewell casing or formation. Sealing such voids may prevent the undesiredflow of fluids (e.g., oil, gas, water, etc.) and/or fine solids into, orfrom, the well bore.

The sealing of such voids, whether or not made deliberately, has beenattempted by introducing a substance into the void and permitting it toremain therein to seal the void. If the substance does not fit into thevoid, a bridge, patch, or sheath may be formed over the void to possiblyproduce a termination of the undesired fluid flow. Substances usedheretofore in methods to terminate the undesired passage of fluidsthrough such voids include settable compositions comprising water andhydraulic cement, wherein the methods employ hydraulic pressure to forcethe settable composition into the void. Once placed into the void, thesettable composition may be permitted to harden.

Remedial cementing operations also may be used to seal portions ofsubterranean formations or portions of gravel packs. The portions of thesubterranean formation may include permeable portions of a formation andfractures (natural or otherwise) in the formation and other portions ofthe formation that may allow the undesired flow of fluid into, or from,the well bore. The portions of the gravel pack include those portions ofthe gravel pack, wherein it is desired to prevent the undesired flow offluids into, or from, the well bore. A “gravel pack” is a term commonlyused to refer to a volume of particulate materials (such as sand) placedinto a well bore to at least partially reduce the migration ofunconsolidated formation particulates into the well bore. Whilescreenless gravel packing operations are becoming more common, gravelpacking operations commonly involve placing a gravel pack screen in thewell bore neighboring a desired portion of the subterranean formation,and packing the surrounding annulus between the screen and the well borewith particulate materials that are sized to prevent and inhibit thepassage of formation solids through the gravel pack with producedfluids. Among other things, this method may allow sealing of the portionof the gravel pack to prevent the undesired flow of fluids withoutrequiring the gravel pack's removal.

Settable compositions also may be used during the drilling of the wellbore in a subterranean formation. For example, in the drilling of a wellbore, it may be desirable, in some instances, to change the direction ofthe well bore. In some instances, settable compositions may be used tofacilitate this change of direction, for example, by drilling a pilothole in a hardened mass of cement, commonly referred to as a “kickoffplug,” placed in the well bore.

Certain formations may cause the drill bit to drill in a particulardirection. For example, in a vertical well, this may result in anundesirable well bore deviation from vertical. In a directional well(which is drilled at an angle from vertical), after drilling an initialportion of the well bore vertically, the direction induced by theformation may make following the desired path difficult. In those andother instances, special directional drilling tools may be used, such asa whipstock, a bent sub-downhole motorized drill combination, and thelike. Generally, the directional drilling tool or tools used may beorientated so that a pilot hole is produced at the desired angle to theprevious well bore in a desired direction. When the pilot hole has beendrilled for a short distance, the special tool or tools are removed, ifrequired, and drilling along the new path may be resumed. To help ensurethat the subsequent drilling follows the pilot hole, it may be necessaryto drill the pilot hole in a kickoff plug, placed in the well bore. Inthose instances, prior to drilling the pilot hole, a settablecomposition may be introduced into the well bore and allowed to set toform a kickoff plug therein. The pilot hole then may be drilled in thekickoff plug, and the high strength of the kickoff plug helps ensurethat the subsequent drilling proceeds in the direction of the pilothole.

Settable compositions used heretofore commonly comprise Portland cement.Portland cement generally is a major component of the cost for thesettable compositions. To reduce the cost of such settable compositions,other components may be included in the settable composition in additionto, or in place of, the Portland cement. Such components may include flyash, slag cement, shale, metakaolin, micro-fine cement, and the like.“Fly ash,” as that term is used herein, refers to the residue from thecombustion of powdered or ground coal, wherein the fly ash carried bythe flue gases may be recovered, for example, by electrostaticprecipitation. “Slag,” as that term is used herein, refers to agranulated, blast furnace by-product formed in the production of castiron and generally comprises the oxidized impurities found in iron ore.Slag cement generally comprises slag and a base, for example, such assodium hydroxide, sodium bicarbonate, sodium carbonate, or lime, toproduce a settable composition that, when combined with water, may setto form a hardened mass.

During the manufacture of cement, a waste material commonly referred toas “CKD” is generated. “CKD,” as that term is used herein, refers to apartially calcined kiln feed which is removed from the gas stream andcollected in a dust collector during the manufacture of cement. Usually,large quantities of CKD are collected in the production of cement thatare commonly disposed of as waste. Disposal of the waste CKD can addundesirable costs to the manufacture of the cement, as well as theenvironmental concerns associated with its disposal. The chemicalanalysis of CKD from various cement manufactures varies depending on anumber of factors, including the particular kiln feed, the efficienciesof the cement production operation, and the associated dust collectionsystems. CKD generally may comprise a variety of oxides, such as SiO₂,Al₂O₃, Fe₂O₃, CaO, MgO, SO₃, Na₂O, and K₂O.

SUMMARY

The present invention relates to cementing operations and, moreparticularly, to settable compositions comprising hydraulic cement, CKD,swellable particles, and water and associated methods of use.

In one embodiment, the present invention provides a method comprising:introducing a settable composition into a subterranean formation,wherein the settable composition comprises a cementitious componentcomprising a hydraulic cement and CKD; a swellable particle; and water;and allowing the settable composition to set in the subterraneanformation.

Another embodiment of the present invention provides a methodcomprising: introducing a settable composition into an annulus between apipe string and a subterranean formation, wherein the settablecomposition comprises a cementitious component comprising a hydrauliccement and CKD; a swellable particle; and water; and allowing thesettable composition to set in the annulus.

Another embodiment of the present invention provides a settablecomposition comprising a cementitious component comprising a hydrauliccement and CKD; a swellable particle; and water.

The features and advantages of the present invention will be apparent tothose skilled in the art. While numerous changes may be made by thoseskilled in the art, such changes are within the spirit of the invention.

BRIEF DESCRIPTION OF THE DRAWINGS

The patent or application file contains at least one drawing executed incolor. Copies of this patent or patent application publication withcolor drawing(s) will be provided by the Office upon request and paymentof the necessary fee. These drawings illustrate certain aspects of someof the embodiments of the present invention, and should not be used tolimit or define the invention.

FIG. 1 is a photograph of a set cement cube comprising cement, cementkiln dust, and a water-swellable polymer, in accordance with oneembodiment of the present invention.

FIG. 2 is a photograph of the set cement cube of FIG. 3 after immersionin a water bath for twenty-four hours, in accordance with one embodimentof the present invention.

FIG. 3 is a photograph of a set cement cube comprising cement, cementkiln dust, and a water-swellable polymer, in accordance with oneembodiment of the present invention.

FIG. 4 is a photograph of the set cement cube of FIG. 5 after immersionin a water bath for twenty-four hours, in accordance with one embodimentof the present invention.

FIG. 5 is a photograph of a set cement cube comprising cement, cementkiln dust, and an oil-swellable elastomer, in accordance with oneembodiment of the present invention.

FIG. 6 is a photograph of the set cement cube of FIG. 7 after immersionin an oil bath for twenty-four hours, in accordance with one embodimentof the present invention.

DESCRIPTION OF PREFERRED EMBODIMENTS

The present invention relates to cementing operations and, moreparticularly, to settable compositions comprising CKD, hydraulic cement,a swellable particle, and water and associated methods of use. Thesettable compositions of the present invention may be used in a varietyof subterranean applications, including primary cementing, remedialcementing, and drilling operations.

Settable Compositions of the Present Invention

In one embodiment, a settable composition of the present inventioncomprises a cementitious component comprising a hydraulic cement andCKD, swellable particles, and water. In some embodiments, a settablecomposition of the present invention may be foamed, for example,comprising water, a cementitious component comprising a hydraulic cementand CKD, a swellable particle, a gas, and a surfactant. A foamedsettable composition may be used, for example, where it is desired forthe settable composition to be lightweight. Other optional additives mayalso be included in the settable compositions of the present inventionas desired, including, but not limited to, hydraulic cement, fly ash,slag cement, shale, zeolite, metakaolin, combinations thereof, and thelike.

The settable compositions of the present invention should have a densitysuitable for a particular application as desired by those of ordinaryskill in the art, with the benefit of this disclosure. In someembodiments, the settable compositions of the present invention may havea density in the range of from about 8 pounds per gallon (“ppg”) toabout 16 ppg. In the foamed embodiments, the foamed settablecompositions of the present invention may have a density in the range offrom about 8 ppg to about 13 ppg.

The water used in the settable compositions of the present invention mayinclude freshwater, saltwater (e.g., water containing one or more saltsdissolved therein), brine (e.g., saturated saltwater produced fromsubterranean formations), seawater, or combinations thereof. Generally,the water may be from any source, provided that it does not contain anexcess of compounds that may adversely affect other components in thesettable composition. In some embodiments, the water may be included inan amount sufficient to form a pumpable slurry. In some embodiments, thewater may be included in the settable compositions of the presentinvention in an amount in the range of from about 40% to about 200% byweight of the cementitious component. In some embodiments, the water maybe included in an amount in the range of from about 40% to about 150% byweight of the cementitious component.

Embodiments of the settable compositions of the present inventioncomprise a cementitious component that comprises CKD. The CKD should beincluded in the settable compositions in an amount sufficient to providethe desired compressive strength, density, and/or cost reduction. Insome embodiments, the CKD may be present in the settable compositions ofthe present invention in an amount of at least 25% by weight of thecementitious component. As used herein, the term “cementitiouscomponent” shall include the hydraulic cement and CKD. In someembodiments, the CKD may be present in the settable compositions of thepresent invention in an amount in the range of from about 25% to about75% by weight of the cementitious component. In some embodiments, theCKD may be present in the settable compositions of the present inventionin an amount in the range of from about 25% to about 50% by weight ofthe cementitious component.

Embodiments of the settable compositions of the present inventioncomprise a cementitious component that also comprises a hydrauliccement. A variety of hydraulic cements may be utilized in accordancewith the present invention, including, but not limited to, thosecomprising calcium, aluminum, silicon, oxygen, iron, and/or sulfur,which set and harden by reaction with water. Suitable hydraulic cementsinclude, but are not limited to, Portland cements, pozzolana cements,gypsum cements, high alumina content cements, slag cements, silicacements, and combinations thereof. In certain embodiments, the hydrauliccement may comprise a Portland cement. In some embodiments, the Portlandcements that are suited for use in the present invention are classifiedas Classes A, C, H, and G cements according to American PetroleumInstitute, API Specification for Materials and Testing for Well Cements,API Specification 10, Fifth Ed., Jul. 1, 1990.

The hydraulic cement generally may be included in the settablecompositions in an amount sufficient to provide the desired compressivestrength, density, and/or cost. In some embodiments, the hydrauliccement may be present in the settable compositions of the presentinvention in an amount of at least 25% by weight of the cementitiouscomponent. In some embodiments, the hydraulic cement may be present inthe settable compositions of the present invention in an amount in therange of from about 25% to about 75% by weight of the cementitiouscomponent. In some embodiments, the hydraulic cement may be present inthe settable compositions of the present invention in an amount in therange of from about 50% to about 75% by weight of the cementitiouscomponent.

In some embodiments, a pozzolana cement that may be suitable for usecomprises fly ash. A variety of fly ashes may be suitable, including flyash classified as Class C and Class F fly ash according to AmericanPetroleum Institute, API Specification for Materials and Testing forWell Cements, API Specification 10, Fifth Ed., Jul. 1, 1990. Class C flyash comprises both silica and lime so that, when mixed with water, itsets to form a hardened mass. Class F fly ash generally does not containsufficient lime, so an additional source of calcium ions is required forthe Class F fly ash to form a settable composition with water. In someembodiments, lime may be mixed with Class F fly ash in an amount in therange of from about 0.1% to about 25% by weight of the fly ash. In someinstances, the lime may be hydrated lime. Suitable examples of fly ashinclude, but are not limited to, “POZMIX® A” cement additive,commercially available from Halliburton Energy Services, Inc., Duncan,Okla.

Where present, the fly ash generally may be included in the settablecompositions in an amount sufficient to provide the desired compressivestrength, density, and/or cost. In some embodiments, the fly ash may bepresent in the settable compositions of the present invention in anamount in the range of from about 5% to about 75% by weight of thecementitious component. In some embodiments, the fly ash may be presentin the settable compositions of the present invention in an amount inthe range of from about 10% to about 60% by weight of the cementitiouscomponent.

In some embodiments, a slag cement that may be suitable for use maycomprise slag. Slag generally does not contain sufficient basicmaterial, so slag cement further may comprise a base to produce asettable composition that may react with water to set to form a hardenedmass. Examples of suitable sources of bases include, but are not limitedto, sodium hydroxide, sodium bicarbonate, sodium carbonate, lime, andcombinations thereof.

Where present, the slag cement generally may be included in the settablecompositions in an amount sufficient to provide the desired compressivestrength, density, and/or cost. In some embodiments, the slag cement maybe present in the settable compositions of the present invention in anamount in the range of from 0% to about 75% by weight of thecementitious component. In some embodiments, the slag cement may bepresent in the settable compositions of the present invention in anamount in the range of from about 25% to about 50% by weight of thecementitious component.

Embodiments of the settable compositions of the present invention maycomprise swellable particles. As used herein, a particle ischaracterized as swelling when it swells upon contact with oil and/or anaqueous fluid (e.g., water). Swellable particles suitable for use inembodiments of the present invention may generally swell by up to about50% of their original size at the surface. Under downhole conditions,this swelling may be more, or less, depending on the conditionspresented. For example, the swelling may be at least 10% at downholeconditions. In some embodiments, the swelling may be up to about 50%under downhole conditions. However, as those of ordinary skill in theart, with the benefit of this disclosure, will appreciate, the actualswelling when the swellable particles are included in a settablecomposition may depend on, for example, the concentration of theswellable particles included in the settable composition. In accordancewith embodiments of the present invention, the swellable particles maybe included in the settable composition, for example, to counteract theformation of cracks in the cement sheath and/or micro-annulus betweenthe cement sheath and the pipe string or the formation. In general, theswellable particles should be capable of swelling when contacted byaqueous fluids and/or oil to inhibit fluid flow through the crack and/ormicro-annulus. Accordingly, the swellable particles may prevent and/orreduce the loss of zonal isolation in spite of the formation of cracksand/or micro-annulus, potentially resulting in an improved annular sealfor the extended cement compositions.

An example of swellable particles that may be utilized in embodiments ofthe present invention comprises a swellable elastomer. Some specificexamples of suitable swellable elastomers include, but are not limitedto, natural rubber, acrylate butadiene rubber, polyacrylate rubber,isoprene rubber, choloroprene rubber, butyl rubber (IIR), brominatedbutyl rubber (BIIR), chlorinated butyl rubber (CIIR), chlorinatedpolyethylene (CM/CPE), neoprene rubber (CR), styrene butadiene copolymerrubber (SBR), sulphonated polyethylene (CSM), ethylene acrylate rubber(EAM/AEM), epichlorohydrin ethylene oxide copolymer (CO, ECO),ethylene-propylene rubber (EPM and EDPM), ethylene-propylene-dieneterpolymer rubber (EPT), ethylene vinyl acetate copolymer,fluorosilicone rubbers (FVMQ), silicone rubbers (VMQ), poly2,2,1-bicyclo heptene (polynorborneane), and alkylstyrene. One exampleof a suitable swellable elastomer comprises a block copolymer of astyrene butadiene rubber. Examples of suitable elastomers that swellwhen in contact with oil include, but are not limited to, nitrile rubber(NBR), hydrogenated nitrile rubber (HNBR, HNS), fluoro rubbers (FKM),perfluoro rubbers (FFKM), tetrafluorethylene/propylene (TFE/P),isobutylene maleic anhydride. Combinations of suitable swellableelastomers may also be used. Other swellable elastomers that behave in asimilar fashion with respect to oil or aqueous fluids also may besuitable. Those of ordinary skill in the art, with the benefit of thisdisclosure, will be able to select an appropriate swellable elastomerfor use in embodiments of the settable compositions of the presentinvention based on a variety of factors, including the application inwhich the composition will be used and the desired swellingcharacteristics.

An example of swellable particles that may be utilized in embodiments ofthe present invention comprises a water-swellable polymer. Some specificexamples of suitable water-swellable polymers, include, but are notlimited to starch-polyacrylate acid graft copolymer and salts thereof,polyethylene oxide polymer, carboxymethyl cellulose type polymers,polyacrylamide, poly(acrylic acid) and salts thereof, poly(acrylicacid-co-acrylamide) and salts thereof, graft-poly(ethylene oxide) ofpoly(acrylic acid) and salts thereof, poly(2-hydroxyethyl methacrylate),and poly(2-hydroxypropyl methacrylate). Combinations of suitablewater-swellable polymers may also be used. In certain embodiments, thewater-swellable polymers may be crosslinked and/or lightly crosslinked.Other water-swellable polymers that behave in a similar fashion withrespect to aqueous fluids also may be suitable. Those of ordinary skillin the art, with the benefit of this disclosure, will be able to selectappropriate water-swellable polymers for use in embodiments of thesettable compositions of the present invention based on a variety offactors, including the application in which the composition will be usedand the desired swelling characteristics.

Where used, the swellable particles generally may be included in thesettable compositions in an amount sufficient to provide the desiredmechanical properties. In some embodiments, the swellable particles maybe present in the settable compositions in an amount up to about 25% byweight of the cementitious component. In some embodiments, the swellableparticles may be present in the settable compositions in a range ofabout 5% to about 25% by weight of the cementitious component. In someembodiments, the swellable particles may be present in the settablecompositions in a range of about 15% to about 20% by weight of thecementitious component.

In addition, the swellable particles that are utilized may have a widevariety of shapes and sizes of individual particles suitable for use inaccordance with embodiments of the present invention. By way of example,the swellable particles may have a well-defined physical shape as wellas an irregular geometry, including the physical shape of platelets,shavings, fibers, flakes, ribbons, rods, strips, spheroids, beads,pellets, tablets, or any other physical shape. In some embodiments, theswellable particles may have a particle size in the range of about 5microns to about 1,500 microns. In some embodiments, the swellableparticles may have a particle size in the range of about 20 microns toabout 500 microns. However, particle sizes outside these defined rangesalso may be suitable for particular applications.

In certain embodiments, the settable compositions of the presentinvention further may comprise metakaolin. Generally, metakaolin is awhite pozzolan that may be prepared by heating kaolin clay, for example,to temperatures in the range of from about 600° to about 800° C. In someembodiments, the metakaolin may be present in the settable compositionsof the present invention in an amount in the range of from about 5% toabout 75% by weight of the cementitious component. In some embodiments,the metakaolin may be present in an amount in the range of from about 5%to about 25% by weight of the cementitious component. In someembodiments, the metakaolin may be present in an amount in the range offrom about 10% to about 50% by weight of the cementitious component.

In certain embodiments, the settable compositions of the presentinvention further may comprise shale. Among other things, shale includedin the settable compositions may react with excess lime to form asuitable cementing material, for example, calcium silicate hydrate. Avariety of shales are suitable, including those comprising silicon,aluminum, calcium, and/or magnesium. An example of a suitable shalecomprises vitrified shale. Suitable examples of vitrified shale include,but are not limited to, “PRESSUR-SEAL® FINE LCM” material and“PRESSUR-SEAL® COARSE LCM” material, which are commercially availablefrom TXI Energy Services, Inc., Houston, Tex. Generally, the shale mayhave any particle size distribution as desired for a particularapplication. In certain embodiments, the shale may have a particle sizedistribution in the range of from about 37 micrometers to about 4,750micrometers.

Where present, the shale may be included in the settable compositions ofthe present invention in an amount sufficient to provide the desiredcompressive strength, density, and/or cost. In some embodiments, theshale may be present in an amount in the range of from about 5% to about75% by weight of the cementitious component. In some embodiments, theshale may be present in an amount in the range of from about 5% to about25% by weight of the cementitious component. In some embodiments, theshale may be present in an amount in the range of from about 10% toabout 35% by weight of the cementitious component. One of ordinary skillin the art, with the benefit of this disclosure, will recognize theappropriate amount of the shale to include for a chosen application.

In certain embodiments, the settable compositions of the presentinvention further may comprise zeolite. Zeolites generally are porousalumino-silicate minerals that may be either a natural or syntheticmaterial. Synthetic zeolites are based on the same type of structuralcell as natural zeolites, and may comprise aluminosilicate hydrates. Asused herein, the term “zeolite” refers to all natural and syntheticforms of zeolite. In some embodiments, the zeolite may be present in thesettable compositions of the present invention in an amount in the rangeof from about 5% to about 65% by weight of the cementitious component.In some embodiments, the zeolite may be present in the settablecompositions of the present invention in an amount in the range of fromabout 5% to about 25% by weight of the cementitious component. Incertain embodiments, the zeolite may be present in an amount in therange of from about 10% to about 40% by weight of the cementitiouscomponent.

In certain embodiments, the settable compositions of the presentinvention further may comprise a set retarding additive. As used herein,the term “set retarding additive” refers to an additive that retards thesetting of the settable compositions of the present invention. Examplesof suitable set retarding additives include, but are not limited to,ammonium, alkali metals, alkaline earth metals, metal salts ofsulfoalkylated lignins, hydroxycarboxy acids, copolymers that compriseacrylic acid or maleic acid, and combinations thereof. One example of asuitable sulfoalkylate lignin comprises a sulfomethylated lignin.Suitable set retarding additives are disclosed in more detail in UnitedStates Pat. No. Re. 31,190, the entire disclosure of which isincorporated herein by reference. Suitable set retarding additives arecommercially available from Halliburton Energy Services, Inc. under thetradenames “HR® 4,” “HR® 5,” HR® 7,” “HR® 12,” “HR® 15,” HR® 25,” “SCR™100,” and “SCR™ 500.” Generally, where used, the set retarding additivemay be included in the settable compositions of the present invention inan amount sufficient to provide the desired set retardation. In someembodiments, the set retarding additive may be present in an amount inthe range of from about 0. 1% to about 5% by weight of the cementitiouscomponent.

Optionally, other additional additives may be added to the settablecompositions of the present invention as deemed appropriate by oneskilled in the art, with the benefit of this disclosure. Examples ofsuch additives include, but are not limited to, accelerators, weightreducing additives, heavyweight additives, lost circulation materials,filtration control additives, dispersants, and combinations thereof.Suitable examples of these additives include crystalline silicacompounds, amorphous silica, salts, fibers, hydratable clays,microspheres, pozzolan lime, latex cement, thixotropic additives,combinations thereof and the like.

An example of a settable composition of the present invention maycomprise a cementitious component comprising a hydraulic cement and CKD,a swellable elastomer, and water. As desired by one of ordinary skill inthe art, with the benefit of this disclosure, such settable compositionof the present invention further may comprise any of the above-listedadditives, as well any of a variety of other additives suitable for usein subterranean applications.

Another example of a settable composition of the present invention maycomprise a cementitious component comprising a hydraulic cement and CKD,a swellable elastomer, water, and an additive comprising at least one ofthe following group: fly ash; shale; zeolite; slag cement; metakaolin;and combinations thereof. As desired by one of ordinary skill in theart, with the benefit of this disclosure, such settable composition ofthe present invention further may comprise any of the above-listedadditives, as well any of a variety of other additives suitable for usein subterranean applications.

As mentioned previously, in certain embodiments, the settablecompositions of the present invention may be foamed with a gas. In someembodiments, foamed settable compositions of the present invention maycomprise a hydraulic cement, CKD, a swellable elastomer, water, a gas,and a surfactant. Other suitable additives, such as those discussedpreviously, also may be included in the foamed settable compositions ofthe present invention as desired by those of ordinary skill in the art,with the benefit of this disclosure. The gas used in the foamed settablecompositions of the present invention may be any gas suitable forfoaming a settable composition, including, but not limited to, air,nitrogen, or combinations thereof. Generally, the gas should be presentin the foamed settable compositions of the present invention in anamount sufficient to form the desired foam. In certain embodiments, thegas may be present in the foamed settable compositions of the presentinvention in an amount in the range of from about 10% to about 80% byvolume of the composition.

Where foamed, the settable compositions of the present invention furthercomprise a surfactant. In some embodiments, the surfactant comprises afoaming and stabilizing surfactant. As used herein, a “foaming andstabilizing surfactant composition” refers to a composition thatcomprises one or more surfactants and, among other things, may be usedto facilitate the foaming of a settable composition and also maystabilize the resultant foamed settable composition formed therewith.Any suitable foaming and stabilizing surfactant composition may be usedin the settable compositions of the present invention. Suitable foamingand stabilizing surfactant compositions may include, but are not limitedto: mixtures of an ammonium salt of an alkyl ether sulfate, acocoamidopropyl betaine surfactant, a cocoamidopropyl dimethylamineoxide surfactant, sodium chloride, and water; mixtures of an ammoniumsalt of an alkyl ether sulfate surfactant, a cocoamidopropylhydroxysultaine surfactant, a cocoamidopropyl dimethylamine oxidesurfactant, sodium chloride, and water; hydrolyzed keratin; mixtures ofan ethoxylated alcohol ether sulfate surfactant, an alkyl or alkeneamidopropyl betaine surfactant, and an alkyl or alkene dimethylamineoxide surfactant; aqueous solutions of an alpha-olefinic sulfonatesurfactant and a betaine surfactant; and combinations thereof. In onecertain embodiment, the foaming and stabilizing surfactant compositioncomprises a mixture of an ammonium salt of an alkyl ether sulfate, acocoamidopropyl betaine surfactant, a cocoamidopropyl dimethylamineoxide surfactant, sodium chloride, and water. A suitable example of sucha mixture is “ZONESEAL® 2000” foaming additive, commercially availablefrom Halliburton Energy Services, Inc. Suitable foaming and stabilizingsurfactant compositions are described in U.S. Pat. Nos. 6,797,054,6,547,871, 6,367,550, 6,063,738, and 5,897,699, the entire disclosuresof which are incorporated herein by reference.

Generally, the surfactant may be present in the foamed settablecompositions of the present invention in an amount sufficient to providea suitable foam. In some embodiments, the surfactant may be present inan amount in the range of from about 0.8% and about 5% by volume of thewater (“bvow”).

Methods of the Present Invention

The settable compositions of the present invention may be used in avariety of subterranean applications, including, but not limited to,primary cementing, remedial cementing, and drilling operations.

An example of a method of the present invention comprises providing asettable composition of the present invention comprising a cementitiouscomponent comprising a hydraulic cement and CKD, a swellable particle,and water; placing the settable composition in a subterranean formation;and allowing the settable composition to set. In some embodiments, thesettable compositions of the present invention may be foamed. As desiredby one of ordinary skill in the art, with the benefit of thisdisclosure, the settable compositions of the present invention useful inthis method further may comprise any of the above-listed additives, aswell any of a variety of other additives suitable for use insubterranean applications.

Another example of a method of the present invention is a method ofcementing a pipe string (e.g., casing, expandable casing, liners, etc.)disposed in a well bore. An example of such a method may compriseproviding a settable composition of the present invention comprising acementitious component comprising a hydraulic cement and CKD, aswellable particle, and water; introducing the settable composition intoan annulus between the pipe string and a subterranean formationsurrounding the well bore; and allowing the settable composition to setin the annulus. Generally, in most instances, the set composition shouldfix the pipe string in the well bore. In some embodiments, the settablecompositions of the present invention may be foamed. As desired by oneof ordinary skill in the art, with the benefit of this disclosure, thesettable compositions of the present invention useful in this methodfurther may comprise any of the above-listed additives, as well any of avariety of other additives suitable for use in subterranean application.

Another example of a method of the present invention is method ofsealing a portion of a gravel pack or a portion of a subterraneanformation. An example of such a method may comprise providing a settablecomposition of the present invention comprising a cementitious componentcomprising a hydraulic cement and CKD, a swellable particle, and water;introducing the settable composition into the portion of the gravel packor the portion of the subterranean formation; and allowing the settablecomposition to form a hardened mass in the portion. The portions of thesubterranean formation may include permeable portions of the formationand fractures (natural or otherwise) in the formation and other portionsof the formation that may allow the undesired flow of fluid into, orfrom, the well bore. The portions of the gravel pack include thoseportions of the gravel pack, wherein it is desired to prevent theundesired flow of fluids into, or from, the well bore. Among otherthings, this method may allow the sealing of the portion of the gravelpack to prevent the undesired flow of fluids without requiring thegravel pack's removal. In some embodiments, the settable compositions ofthe present invention may be foamed. As desired by one of ordinary skillin the art, with the benefit of this disclosure, the settablecompositions of the present invention useful in this method further maycomprise any of the above-listed additives, as well any of a variety ofother additives suitable for use in subterranean applications.

Another example of a method of the present invention is a method ofsealing voids located in a pipe string (e.g., casing, expandablecasings, liners, etc.) or in a cement sheath. Generally, the pipe stringwill be disposed in a well bore, and the cement sheath may be located inthe annulus between the pipe string disposed in the well bore and a wallof the well bore. An example of such a method may comprise providing asettable composition of the present invention comprising a cementitiouscomponent comprising a hydraulic cement and CKD, a swellable particle,and water; introducing the settable composition into the void; andallowing the settable composition to set to form a hardened mass in thevoid. In some embodiments, the settable compositions of the presentinvention may be foamed. As desired by one of ordinary skill in the art,with the benefit of this disclosure, the settable compositions of thepresent invention useful in this method further may comprise any of theabove-listed additives, as well any of a variety of other additivessuitable for use in subterranean applications.

When sealing a void in a pipe string, the methods of the presentinvention, in some embodiments, further may comprise locating the voidin the pipe string; and isolating the void by defining a space withinthe pipe string in communication with the void; wherein the settablecomposition may be introduced into the void from the space. The void maybe isolated using any suitable technique and/or apparatus, includingbridge plugs, packers, and the like. The void in the pipe string may belocated using any suitable technique.

When sealing a void in the cement sheath, the methods of the presentinvention, in some embodiments, further may comprise locating the voidin the cement sheath; producing a perforation in the pipe string thatintersects the void; and isolating the void by defining a space withinthe pipe string in communication with the void via the perforation,wherein the settable composition is introduced into the void via theperforation. The void in the pipe string may be located using anysuitable technique. The perforation may be created in the pipe stringusing any suitable technique, for example, perforating guns. The voidmay be isolated using any suitable technique and/or apparatus, includingbridge plugs, packers, and the like.

Another example of a method of the present invention is a method ofchanging the direction of drilling a well bore. An example of such amethod may comprise providing a settable composition of the presentinvention comprising a cementitious component comprising a hydrauliccement and CKD, a swellable particle, and water; introducing thesettable composition into the well bore at a location in the well borewherein the direction of drilling is to be changed; allowing thesettable composition to set to form a kickoff plug in the well bore;drilling a hole in the kickoff plug; and drilling of the well borethrough the hole in the kickoff plug. In some embodiments, the settablecompositions of the present invention may be foamed. As desired by oneof ordinary skill in the art, with the benefit of this disclosure, thesettable compositions of the present invention useful in this methodfurther may comprise any of the above-listed additives, as well any of avariety of other additives suitable for use in subterraneanapplications.

Generally, the drilling operation should continue in the direction ofthe hole drilled through the kickoff plug. The well bore and hole in thekickoff plug may be drilled using any suitable technique, includingrotary drilling, cable tool drilling, and the like. In some embodiments,one or more oriented directional drilling tools may be placed adjacentto the kickoff plug. Suitable directional drilling tools include, butare not limited to, whip-stocks, bent sub-downhole motorized drillcombinations, and the like. The direction drilling tools then may beused to drill the hole in the kickoff plug so that the hole ispositioned in the desired direction. Optionally, the directionaldrilling tool may be removed from the well bore subsequent to drillingthe hole in the kickoff plug.

To facilitate a better understanding of the present invention, thefollowing examples of certain aspects of some embodiments are given. Inno way should the following examples be read to limit, or define, thescope of the invention.

EXAMPLE 1

To evaluate the use of particles which swell in the presence of anaqueous fluid, a slurry was prepared containing 50% class A cement and50% class A CKD. The slurry had a density of 13.2 ppg. Water-swellablepolymer particles (sodium salt of poly(acrylic acid), lightlycrosslinked, available from Aldrich, Milwaukee, Wis.) were added to thisslurry in an amount of 20% by weight of the cement and CKD. Thecomposition was poured into a cube and cured at room temperature for 24hours. Thereafter, the cube was cut in half. FIG. 1 is a photograph ofthe halved cube taken with a stereomicroscope. The halved cube was thensubmerged in a water bath at room temperature. After 24 hours, thehalved cube was removed from the water bath and photographed using thestereomicroscope. FIG. 2 is a photograph of the halved cube afterimmersion in the water bath for 24 hours. As illustrated by FIG. 4, thewater-swellable polymer particles swelled in the presence of the water.

EXAMPLE 2

To further evaluate the use of particles which swell in the presence ofan aqueous fluid, a slurry was prepared containing 50% class A cementand 50% class A CKD. The slurry had a density of 13.2 ppg.Water-swellable polymer particles (sodium salt graft-poly(ethyleneoxide) of poly(acrylic acid), crosslinked, available from Aldrich,Milwaukee, Wis.) were added to this slurry in an amount of 20% by weightof the cement and CKD. The composition was poured into a cube and curedat room temperature for 24 hours. Thereafter, the cube was cut in half.FIG. 3 is a photograph of the halved cube taken with a stereomicroscope.The halved cube was then submerged in a water bath at room temperature.After 24 hours, the halved cube was removed from the water bath andphotographed using the stereomicroscope. FIG. 4 is a photograph of thehalved cube after immersion in the water bath for 24 hours. Asillustrated by FIG. 4, the water-swellable polymer particles swelled inthe presence of the water.

EXAMPLE 3

To evaluate the use of particles which swell in the presence of oil, aslurry was prepared containing 50% class A cement and 50% class A CKD.To this slurry, oil-swellable elastomer particles (block copolymer ofstyrene-butadiene) were in an amount of 10% by weight of the cement andCKD. The composition had a density of 13.2 ppg. The composition waspoured into three cubes, and the cubes were cured for 24 hours at roomtemperature. The cured cubes were measured for dimension and weight. Thecubes were then submerged in a mineral oil bath. At the end of fixedperiods of time, the cubes were weighed and the dimensions of the cubeswere measured. Based on the weights of the cubes, the average amount ofexpansion was found to be 0.06% over 53 days. It is believed thatincreased cube weight was due to swelling of the elastomer particlesfrom contact with the mineral oil. It is further believed that theswelling of the elastomer particles fills the porosity of the cubes. Theexpansion data for the cubes is set forth in the table below.

TABLE 1 Day Cube # Width (cm) Height (cm) Weight (g) 1 1 5.08 5.11222.96 2 5.08 5.13 226.86 3 5.13 5.08 227.53 4 1 5.08 5.13 222.73 2 5.115.13 226.74 3 5.13 5.11 227.32 7 1 5.13 5.11 222.85 2 5.11 5.13 226.79 35.13 5.11 227.43 12 1 5.13 5.08 222.98 2 5.11 5.13 226.94 3 5.11 5.16227.68 25 1 5.08 5.13 223.31 2 5.08 5.13 227.22 3 5.08 5.13 228 32 15.11 5.13 223.25 2 5.11 5.13 227.16 3 5.08 5.13 227.97 39 1 5.08 5.13223.04 2 5.11 5.13 226.8 3 5.11 5.13 227.72 46 1 5.08 5.11 223.37 2 5.085.13 227.11 3 5.13 5.08 227.9 53 1 5.08 5.13 223.16 2 5.11 5.13 226.9 35.13 5.11 227.72

EXAMPLE 4

To further evaluate the use of particles which swell in the presence ofoil, a slurry was prepared containing 50% class A cement and 50% class ACKD. The slurry had a density of 13.5 ppg. Oil-swellable polymerparticles (block copolymer of styrene-butadiene elastomer particles)were added to this slurry in an amount of 20% by weight of the cementand CKD. The composition was poured into three cubes, and the cubes werecured for 24 hours at room temperature. The cured cubes were measuredfor dimension and weight. The cured cubes were then submerged in amineral oil bath. At the end of fixed periods of time, the cubes wereweighed and the dimensions of the cubes were measured. Based on theweights of the cubes, the average amount of expansion was found to be3.72% over 46 days. It is believed that increased cube weight was due toswelling of the elastomer particles from contact with the mineral oil.It is further believed that the swelling of the elastomer particlesfills the porosity of the cubes. The expansion data for the cubes is setforth in the table below.

TABLE 2 Day Cube # Width (cm) Height (cm) Weight (g) 1 1 5.16 5.11211.23 2 5.08 5.16 210.34 3 5.08 5.13 212.22 6 1 5.16 5.11 214.44 2 5.135.18 213.47 3 5.13 5.18 215.27 13 1 5.13 5.16 215.98 2 5.13 5.16 214.683 5.13 5.21 216.68 19 1 5.13 5.18 216.58 2 5.13 5.16 215.15 3 5.16 5.21217.17 26 1 5.16 5.21 217.51 2 5.13 5.18 215.98 3 5.16 5.21 218.05 33 15.16 5.21 218.45 2 5.13 5.18 216.62 3 5.16 5.23 218.73 40 1 5.16 5.11219.42 2 5.08 5.16 217.5 3 5.08 5.13 219.53 47 1 5.16 5.11 219.97 2 5.135.18 217.82 3 5.13 5.18 219.59

EXAMPLE 5

To further evaluate the use of particles which swell in the presence ofoil, a slurry was prepared containing 50% class A cement and 50% class ACKD. The slurry had a density of 13.2 ppg. Oil-swellable elastomerparticles (block copolymer of styrene-butadiene elastomer particles)were added to this slurry in an amount of 20% by weight of the cementand CKD. The composition was poured into a cube and cured at roomtemperature for 24 hours. Thereafter, the cube was cut in half. FIG. 5is a photograph of the halved cube taken with a stereomicroscope. Thehalved cube was then submerged in a mineral oil bath at roomtemperature. After 24 hours, the halved cube was removed from the oilbath and photographed using the stereomicroscope. FIG. 6 is a photographof the halved cube after immersion in the oil bath for 24 hours. Asillustrated by FIG. 6, the oil-swellable elastomer particles swelled inthe presence of the oil.

EXAMPLE 6

This example was performed to determine whether the expansion of thecubes observed in Examples 1-8 was due to swelling of the elastomerparticles or absorption of the water or mineral oil by the cubes. A 13.2ppg slurry was prepared containing 50% class A cement and 50% class ACKD. No swellable particles were included in this sample composition.The slurry was shaped into a cube, and the cube was cured at roomtemperature for 24 hours. The cured cube was weighed. The cubes werethen submerged in a water bath. After 7 days, the cube was weighedagain. As illustrated in the table below, the cube absorbed aninsignificant amount of water.

TABLE 3 Day Weight (g) 1 206.10 8 206.27

EXAMPLE 7

As a second comparative example, Example 2 was repeated, except that thecubes were submerged in a mineral oil bath. The cubes were weighed aftercuring and again after 7 days. As illustrated in the table below, thecube absorbed an insignificant amount of mineral oil.

TABLE 4 Day Weight (g) 1 203.99 8 204.06

Therefore, the present invention is well adapted to attain the ends andadvantages mentioned as well as those that are inherent therein. Theparticular embodiments disclosed above are illustrative only, as thepresent invention may be modified and practiced in different butequivalent manners apparent to those skilled in the art having thebenefit of the teachings herein. Furthermore, no limitations areintended to the details of construction or design herein shown, otherthan as described in the claims below. It is therefore evident that theparticular illustrative embodiments disclosed above may be altered ormodified and all such variations are considered within the scope andspirit of the present invention. In particular, every range of values(for example, of the form “from about a to about b,” or, “from about ato b,” or, “from a to about b,” or, “from a to b,”) disclosed herein isto be understood as referring to the power set (the set of all subsets)of the respective range of values, and set forth every range encompassedwithin the broader range of values. Moreover, the indefinite articles“a” or “an”, as used in the claims, are defined herein to mean one ormore than one of the element that it introduces. Also, the terms in theclaims have their plain, ordinary meaning unless otherwise explicitlyand clearly defined by the patentee.

1. A method comprising: introducing a settable composition into asubterranean formation, wherein the settable composition comprises: acementitious component comprising: a hydraulic cement, and cement kilndust; a swellable particle; and water; and allowing the settablecomposition to set in the subterranean formation.
 2. The method of claim1 wherein the cement kiln dust is present in the settable composition inan amount of about 25% to about 75% by weight of the cementitiouscomponent, and wherein the hydraulic cement is present in the settablecomposition in an amount of about 50% to about 75% by weight of thecementitious component.
 3. The method of claim 1 wherein the cement kilndust is present in the settable composition in an amount of about 25% toabout 50% by weight of the cementitious component, and wherein thehydraulic cement is present in the settable composition in an amount ofabout 25% to about 75% by weight of the cementitious component.
 4. Themethod of claim 1 wherein the swellable particle is present in thesettable composition in an amount of about 5% to about 25% by weight ofthe cementitious component.
 5. The method of claim 1 wherein theswellable particle is present in the settable composition in an amountof about 15% to about 20% by weight of the cementitious component. 6.The method of claim 1 wherein the swellable particle swells upon contactwith an aqueous fluid.
 7. The method of claim 1 wherein the swellableparticle swells upon contact with oil.
 8. The method of claim 1 whereinthe swellable particle comprises a water-swellable polymer.
 9. Themethod of claim 1 wherein the swellable particle comprises a swellableelastomer.
 10. The method of claim 1 wherein the swellable particlecomprises a block copolymer of styrene butadiene rubber.
 11. The methodof claim 1 wherein the swellable particle comprises a sodium salt ofpolyacrylic acid.
 12. A method comprising: introducing a settablecomposition into an annulus between a pipe string and a subterraneanformation, wherein the settable composition comprises: a cementitiouscomponent comprising: a hydraulic cement, and cement kiln dust; aswellable particle; and water; and allowing the settable composition toset in the annulus.
 13. The method of claim 12 comprising introducingthe pipe string into a well bore that penetrates the subterraneanformation.
 14. The method of claim 12 wherein the cement kiln dust ispresent in the settable composition in an amount of about 25% to about75% by weight of the cementitious component, and wherein the hydrauliccement is present in the settable composition in an amount of about 25%to about 75% by weight of the cementitious component.
 15. The method ofclaim 12 wherein the swellable particle is present in the settablecomposition in an amount of about 5% to about 25% by weight of thecementitious component.
 16. The method of claim 12 wherein the swellableparticle swells upon contact with an aqueous fluid.
 17. The method ofclaim 12 wherein the swellable particle swells upon contact with oil.18. The method of claim 12 wherein the swellable particle comprises ablock copolymer of styrene butadiene rubber.
 19. The method of claim 1wherein the swellable particle comprises a sodium salt of polyacrylicacid.
 20. A method comprising: introducing a settable composition intoan annulus between a pipe string and a subterranean formation, whereinthe settable composition comprises: a cementitious component comprising:a hydraulic cement in an amount of about 25% to about 75% by weight ofthe cementitious component, and cement kiln dust in an amount of about25% to about 75% by weight of the cementitious component; a swellableparticle in an amount of about 5% to about 25% by weight of thecementitious component and comprising at least one swellable polymerselected from the group consisting of a block copolymer of styrenebutadiene rubber, a sodium salt of polyacrylic acid, and combinationsthereof; and water; and allowing the settable composition to set in theannulus.